The brass lamp might be a tough one. The acid is Muriatic Acid which is another name for hydrochloric acid. Brass is an alloy of copper and zinc. Guess what Hydrochloric acid dissolves zinc easily. If the brass has clear varnish on it maybe just that was damaged. If the brass itself was stained you maybe able to polish the stain out. If it's a valuable or antique with a patina you want to save I suggest consulting a conservator.

Not sure about the antique status, it belonged to my mom and I inherited it when she died. But, it is unusual. Only one I have ever seen like it. It is a floor lamp and you pull the entire stem down to turn it on and off. It also has the switch to change which light bulbs go on or off. What do you think?